DSA radio policy-controlled classifier restriction

ABSTRACT

A dynamic spectrum access (DSA) radio communication device includes a plurality of signal classifier modules operating thereon, with each different classifier module able to classify a different radio signal type. A classifier scheduler module is provided to manage classifier use by selecting which classifiers to operate or not to operate and to manage the order that the classifiers are operated in. The communication device is configured to invoke policies that include control elements associated with adjusting the classifier scheduler module. The control elements associated with adjusting the classifier scheduler module tend to reduce the number of classifier cycles required to classify a radio signal. The device includes or can be provided with a plurality of different policies suitable for different radio environments and operating modes. Specifically, different policies may include different classifier control elements suitably matched to the present radio environment and/or operating mode.

1 COPYRIGHT NOTICE

A portion of the disclosure of this patent document may contain materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever. The following notice shall apply to this document:Copyright 2014-2015, Shared Spectrum Company.

2 BACKGROUND OF THE INVENTION 2.1 Field of the Invention

The illustrative, illustrative technology herein relates to systems,software, and methods for policy-controlled restriction of classifieruse by Dynamic Spectrum Access (DSA) Radios.

The technology herein has applications in the areas of DSA Radio designand operation and the ability to change radio operation according to oneor more situational changes.

2.2 The Related Art

Radio frequency (RF) spectrum is a limited resource in high demand thatmust be shared by all of those needing to make use of it. Withincreasing use of cell phones, Wi-Fi networks, Bluetooth devices,remotely operated vehicles, and other users of RF spectrum, efficientuse of the available RF spectrum is increasingly important, and pastpractices, such as setting aside entire bands for specific purposes orusers, such as television (TV), broadcast radio, emergency services,radar, and military use, are wasteful of and make inefficient use ofavailable spectrum. The concept of dynamic spectrum access (DSA) hasbeen created as a way to protect assigned spectrum users (primaryusers), while permitting use of the same spectrum by others (secondaryusers), as long as unacceptable levels of interference with primary useruse of assigned spectrum are avoided. Development of DSA technology isin progress, as are regulatory changes to permit its use.

To avoid unacceptable interference with primary users, conventional DSAdevices detect use of assigned spectrum, determine whether the use isthat of a primary user, and if so, take actions to either avoidcommunication over the in use channel, e.g. by switching to anotherspectrum or channel, or to share the assigned spectrum in a manner thatdoes not interfere with use by the primary user. Examples of sharing thein use spectrum include reducing transmitted power, directingtransmissions along paths that will not cause unacceptable interference,or scheduling secondary communication during temporal breaks in theprimary communication.

FIG. 1 is a diagram of a portion of a conventional DSA device employinga signal detector and a plurality of predefined signal classifiersoperable on a digital processor. Each signal classifier is configured todetermine whether the frequency spectrum or channel being probed by thedetector is occupied or in use by a primary user and if so, which stepsto take if a primary user signal is identified. The received signal datafrom the channel being received by a conventional DSA transceiver isinput (1010) and passed to a signal detector (1020) and also to one ormore classifiers (1030, 1040, & 1050). Each classifier uses a differentclassification method to attempt to classify the detected signal. Thesignal detector (1020) determines whether a signal is present (asopposed to noise), and outputs an indication of signal presence orabsence (1025) to a frequency manager (1060). Output from anyclassifiers that successfully classify the signal (1045) is input, alongwith the output of the signal detector (1025), to the DSA frequencymanagement component (1060) that determines whether a detected signalrequires the current frequency in use to be vacated, or for othermitigating steps, such as power reduction or timing changes, be taken(1080), or not (1070).

OBJECTS OF THE INVENTION

In view of the problems associated with conventional methods andapparatus set forth above, it is an object of the present invention toprovide systems and methods for policy control of classifier use in DSAradios, such control at least comprising means to prevent use ofselected classifiers.

It is also an object of the present invention to provide means forremoving obsolete, malfunctioning, or underperforming classifiers fromservice.

It is also an object of the present invention to provide means formanaging radio resource consumption, such as CPU time or battery power,through management of classifier use.

It is also an object of the present invention to provide methods forclassifier use ordering based on historical data related to classifiersuccess in classifying signals as one means for managing radio resourceconsumption.

3 BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention will best be understood from adetailed description of the invention and example embodiments thereofselected for the purposes of illustration and shown in the accompanyingdrawings in which:

FIG. 1 is a diagram of a portion of a prior art DSA radio employing aplurality of classifiers to classify a signal.

FIG. 2 is a diagram showing components of a DSA enabled devicecomprising aspects of an illustrative embodiment.

FIG. 3 is a diagram or a portion of a DSA radio employing aspects of anillustrative embodiment.

FIG. 4 is a diagram of a portion of an illustrative implementationprocessing a channel with a primary user signal present that isclassifiable under policy by Classifier 1.

FIG. 5 is a diagram of a portion of an illustrative implementationprocessing a channel with a secondary user signal present that isclassifiable under policy by Classifier 3.

FIG. 6 is a diagram of a portion of an illustrative implementationprocessing a channel with no signal present.

FIG. 7 is a diagram of a portion of an illustrative implementationprocessing a channel with a signal present that is not classifiable byany available classifier permitted by policy.

FIG. 8 depicts a flowchart of a possible process for using policycontrolled classifiers for determining whether to mitigate interference.

4 DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

Conventional DSA devices make use of “classifiers” to classify signalsdetected on an assigned spectrum or channel so that a decision can bemade as to whether a detected signal is that of a primary user or asecondary user. Conventional classifiers operate in various ways, suchas analyzing characteristics of the signal (“cyclostationary analysis”),e.g. detecting “beacons” or “pilot signals” within the assigned spectrumthat can be matched to characteristics of a primary user of a particulartype, or matching the detected signal origin or direction to knownprimary user locations. Other conventional classifiers are specializedfor identification of specific signal or noise types, such as TV,cellular telephone, air traffic control radar, or man-made noise (e.g.transmission line noise).

In a conventional operating scenario, a plurality of signal classifiersare preconfigured as components of a conventional DSA radio, with eachsignal classifier operated as part of the frequency selection managementmodule of the DSA radio. When one or more of the classifiers identify aprimary user signal on a particular frequency spectrum or channel, thatchannel is removed from consideration for use by the DSA radio and otherchannels are evaluated. When a DSA radio incorporates a plurality ofclassifiers, all are typically used, in parallel or sequentially, toanalyze a detected signal and classify it as to type. In some DSA radioswith a plurality of classifiers, the available classifiers may be usedsequentially until one classifies a detected signal, or until all havefailed to do so. The sequence of classifier use is typically fixed bythe design of the DSA radio. Such conventional techniques may beinefficient when the available classifier capable of identifying thespecific detected signal is not one of the first classifiers used.Attempting to classify the signal with classifiers that are not capableof classifying it may delay classification and waste DSA radioresources, such as memory, processor cycles, and in mobile devices,battery power. As described herein, embodiments of the present inventionmay provide the ability for a DSA radio to identify a subset ofclassifiers that have a relatively high probability of identifyingdetected signals as primary user signals, to avoid use of those that areincapable of, or unlikely to, produce an identification of detectedprimary user signals at the DSA radio's location, and/or to define theorder in which the identified classifiers are used so that those withthe greatest likelihood of succeeding in identifying signals at the DSAradio's location, or which impose the least resource burden on the DSAradio, are used first.

In addition to the inefficiency of current DSA radio classifier use,there is typically no provision for dynamic update of classifiers toidentify or classify new signal types, or to remove faulty classifiersfrom use. At least some DSA radios support update of the DSA software,which can include updating classifiers, but such updates require a breakin operation of the DSA radio, user intervention, and/or may not happenin a timely manner. Embodiments of the present invention may providevarious capabilities for dynamically removing faulty classifiers fromuse in a timely manner, and without interrupting DSA radio use isneeded.

Referring now to FIG. 2, a non-limiting illustrative schematic diagramshows a channel management module (2000) operating on a DSA enabledradio device according to an embodiment of the present invention. Thechannel management module (2000) includes an antenna (2005) connected toa radio transceiver (2010). For receive-only operations, a transceivermay be replaced with a receive-only module without departing from thescope of the invention. A transceiver controller (2020) in communicationwith the radio transceiver operates to change the operating frequency ofthe transceiver (2010) from one channel to another, to either receive ortransmit radio signal portions over a radio frequency channel selectedby a channel manager (2160).

The DSA enabled radio includes a digital data processor, a portion ofwhich is shown as a channel management sub module (2070). A digital datastorage module (2030) is in communication with the digital dataprocessor. The combined digital data processor and data storage modulecooperatively manage the operation of the DSA radio system tocommunicate with other devices over one or more radio communicationfrequency bands or channels. More specifically, the channel managermodule (2000) dynamically switches communication sessions and/orportions of a communication from one channel to another in order toutilize assigned and unassigned radio frequency spectrum or channelsthat become available for secondary use. In particular, in someoperating modes, the DSA enabled radio system is configured to operateas a secondary user on one or more assigned spectrum channels withoutinterfering with the use of any of the assigned spectrum channels by aprimary user and the depicted channel manager (2000) is configured tomanage channel selection and various aspects of channel sectionaccording to one or more software policies.

The digital data processor module (2070) preferably includes a singlechip microprocessor, a central processing unit (CPU), or the likesuitable for executing user defined loadable software and/or firmwaremodules. The software modules each perform processing tasks suitable foroperating the DSA radio in an operating mode that communicates withother radio devices using dynamic spectrum access techniques outlinedbelow. The data storage module (2030) preferably includes a non-volatilememory device suitable for storing the user defined loadable software orfirmware modules and executing the software or firmware in cooperationwith the digital data processor module. In addition, the data storagemodule (2030) operates to store digital data generated by elements ofthe local device and to communicate with other DSA or non-DSA enabledradio devices, including Wi-Fi enabled devices, and/or to exchange datawith the other devices and/or to receive updates to any software orfirmware module operating on the DSA enabled radio device. Alternately,numerous other well-known digital data processor and data storagemodules, including a unitary device that operates as both a digital dataprocessor and data storage module, are usable without deviating from thepresent invention. In further alternative illustrative embodiments, someor all data processing can be carried out using one or more hardwarecomponents that do not make use of loadable software, such as ASICs(Application Specific Integrated Circuits), FPGAs (Field ProgrammableGate Arrays), or others, without deviating from the present invention.In non-limiting example embodiments the non-volatile data storage module(2030), may comprise flash memory devices, hard disc drives, Read OnlyMemory (ROM), Programmable Read Only Memory (PROM), Erasable Read OnlyMemory (EPROM), Electrically Erasable Programmable Read Only Memory(EEPROM), or combinations of these or other devices.

In operation, the transceiver (2010) is set to operate at a given radiofrequency band or channel by the channel manager (2160). By listening tothe selected channel, the transceiver (2010) generates an analog signalresponsive to any electromagnetic energy present on the channel. Thetransceiver further operates to convert the analog signal to acorresponding digital radio signal and the digital radio signal isconveyed to the data processor module (2070) for processing by one ormore detector modules (2090 &2100) and also by one or more digitalsignal classifier modules (2120 & 2130) for signal classification.Generally, each detector detects the presence of a digital radio signaland its characteristics, e.g. temporal, power amplitude, and spectralcharacteristics, and each classifier classifies the detected signal bycomparing detected signal characteristics with known assigned spectrumuser signal types or protocols, e.g. by classifying the detected signalas an 802.11 Wi-Fi signal, various cellular telephone signals such asLTE, 3G, 4G, a broadcast radio or television signal, a municipal safetyor military signal, an air traffic signal, radar signal, etc.

According to an embodiment of the present invention, the operation ofthe detectors and classifiers are subject to policies managed by apolicy manager module (2170). As shown in FIG. 2, the policy managermodule (2170) receives and interprets policies from a policy storagemodule (2060). The policies may include rules for spectrum use, and assuch directly and indirectly may include rules for operating one or allof the detectors (2090\2100), the classifiers (2120 2130), the channelmanager module (2160) and for operating a policy scheduler (2140), whicheach may be operated in a manner that enforces or implements thespectrum use policy. In addition, the classifier scheduler moduleexchanges digital data with a historical data storage module (2050) asneeded to track classifier schedules and other data useful in managingspectrum use by policy. Historical processing data (2050) may include,for example, times of day and geographic locations at which signals ofspecific types have been detected, and/or a success counts for eachsignal classifiers. The channel management module (2000) may include oneor more digital radio signal sensing components, referred to herein as“detectors” (2090 & 2100), that are configured to process digital radiosignal data received from the transceiver (2010) to detect radio signaltransmissions of other devices in one or more spectral bandwidths orchannels of the radio spectrum.

A DSA-enabled device (2000) can include one or more signal processingcomponents, herein known as “classifiers” (2120 & 2130), which areconfigured to process data from the transceiver (2010) and optionallyfrom one or more detectors (2090 & 2100), and to determine the type ortypes of signal present in the transceiver data. Detectors 2090 and 2100may be provided as part of, or may be external to the DSA transceiver.

The channel management module (2000) may include a component, hereinknown as channel management (2160), which is configured to identifychannels suitable for use by the DSA-enabled device based at least inpart based on output data generated by one or more detectors and/or oneor more classifiers.

The channel management module (2000) may include a component, hereinknown as a classifier scheduler (2140), which is configured to controlthe operation of one or more classifiers according to the requirementsof a given policy.

The channel management module (2000) may include a component, hereinknown as “interference management” (2160), which is configured to usethe outputs of one or more detectors and/or one or more classifiers toprovide input to channel management useful for selection of transmissionchannels that comply with a given policy.

The channel management module (2000) may include a component, hereinknown as “policy management” (2170), which is configured to supply atleast some aspects of policy relevant to each to one or more ofdetectors, classifiers, classifier scheduler, interference management,and channel management and further configured to receive, validate anddetermine the applicability of policy, locally store and locally andnon-locally request policy from policy sources, or other aspects ofpolicy management useful for a DSA enabled device.

FIG. 3, shows a schematic diagram of an illustrative operating mode(3000) suitable for controlling a DSA radio device according to aspectrum use policy (3010) as disclosed herein. In the illustratedexample, the spectrum use policy (3010) includes a classifier plan(3015) which is specified using a classifier plan specificationlanguage. The classifier plan (3015) includes classifier operatingrules, set forth in the policy, for how to classify the signal (3090).The classifier plan (3015) may define a classifier schedule to beimplemented by the classifier scheduler (3020). The classifier schedulemay include details of which classifier to run first, whichclassifier(s) not to run at all, and contingencies for what to do when aclassifier successfully classifies a signal or fails to classify asignal. Additionally, the policy (3010) may include classifier plansthat are dependent on output from the signal detector, such as not toclassify a signal that exceeds an upper power amplitude limit or failsto exceed a lower power amplitude threshold or the like. Accordingly theclassifier scheduler (3020) receives a classifier plan (3015) from thepolicy (3010) and the detector signal (3060). Both inputs may beevaluated in view of the policy (3010) to determine a classifierschedule.

Once the classifier plan and classifier schedule are established, one ormore classifiers (3030, 3040, & 3050) may operate on the signal (3090)under control of the classifier scheduler (3020) in an attempt toclassify the signal. In various classifier scheduler operating modes,some or all of the classifiers may be operated simultaneously or inparallel. Alternatively or in addition, some or all of the classifiersmay be operated in series or asynchronously. When operated in series,the classifier scheduler may dictate the order in which the classifiersare run and which classifiers, if any, should not be run. Once a signalis classified by a classifier and a classification (3130, 3140, or 3150)of the signal (3090) is conveyed to the interference manager, it may bepreferred to halt operation of one, some, or all of any other operatingclassifiers. If all classifiers specified to be operated by theclassifier scheduler fail to classify the signal (3090), theinterference manager (3070) may takes any appropriate action, e.g.switching to another channel. However, other actions may be taken, suchas operating classifiers that were not scheduled to be operated or thelike, and these contingencies may also be set forth in the policy(3010).

As further detailed in FIG. 3, in addition to the classifier results(3130, 3140, 3150), a detector signal (3160) and a policy input (3170)are each conveyed to the interference manager. Accordingly, in someconfigurations the operating mode (3000) may include generating aninterference manager control signal (3080) without invoking any of theclassifiers (3030, 3040, or 3050). In particular, the policy (3010) mayinclude elements for generating a control signal (3080) withoutclassifying the detector signal, such as in cases where the signaldetector (3060) fails to detect a signal that exceeds a lower poweramplitude threshold, thereby indicating that the selected channel can beused without interfering with a primary. In further example operatingmodes, the policy (3010) may include operating modes that further alterthe classifier schedule (3020) or suspend classification altogetherafter an initial signal on a channel has been classified, such as onlyrunning the classifier associated with classifying the classified signaltype, or not running any classifier until characteristics of the signal(3160) indicate sufficient changes in the signal (3090) such as anincrease in power amplitude or unexpected signal temporal or spectralcharacteristics.

Thus, according to some aspects of the illustrative operating mode(3000) described above, the policy (3010) controls the use ofclassifiers in a manner that may reduce classifier operating time andmay decrease the time required to classify a signal (3090). When thepolicy successfully reduces classifier operating time, the time requiredto dynamically access an available communication channel is reduced, thepower required to access an available communication channel is reduced,and processor time is freed up for other activities.

A spectrum use policy (referred to herein as a “policy”) is amachine-interpretable specification that defines the required,permitted, and/or prohibited functionality of a DSA device, and, as usedherein, may specifically defines functionality of channel management.Policies can include one or more policy elements. A policy elementincludes specifications related to at least one aspect of policy. Policyelements of a first policy can comprise references to one or more secondpolicies. Such references can be used to incorporate the secondpolicies, or policy elements from the second policies, into the firstpolicy as if the second policy elements had been incorporated into thefirst policy directly. Policy references can be by location (e.g. a URL,URI, filename, network file location specification, etc.); by name (e.g.“policy-123”) where the location to find the named policy is known, canbe assumed, or where a search mechanism has been defined; or by acombination of these or other methods that will be well understood bythose with skill in the art. Some or all of the policy elements of afirst policy can be combined with some or all of the elements of asecond policy to form a third policy. A policy element may be devicedependent, device capability-dependent, time-dependent, and/orlocation-dependent. A policy element also may vary with user input ordevice authorizations. Devices can be configured with a default policyfor use when no other policy is available, or to define methods toreceive and validate updates to policy from authorized remote devicesthat then partially or completely replace the default policy. Policy canbe distributed by use of hardware devices (e.g. flash drives, ROM chips,disk drives, and DVD-ROM), interfaced with the DSA radio through wiredor wireless networks, through wireless broadcast, or by any other methodor methods deemed proper by those with skill in the art.

Policies can originate with regulators, manufacturers, developers,network and system operators, as well as DSA device users (referred toherein, collectively and individually, as “policy originators”).Policies can be supplied to a DSA device in a number of ways, such asover the air, by way of wired networks, through use of plug in modulesor media, by interaction with a user through a user interface, byincorporation into the device by its design or construction, or othermeans that depend on various factors that will be apparent to those withskill in the art. DSA devices can employ a plurality of methods toacquire policy, such as by incorporating a default policy by design,accepting user input policy via a user interface, and acquiringregulatory policy over the air from a wireless policy server. Due to thepossibly dynamic nature of classifier plans, policy distribution andupdate methods that support dynamic policy adjustments may be preferredfor use.

Policies as disclosed herein can be universally applicable to all DSAradio devices, can be specific to a class of DSA radio devices, or candiffer for each specific DSA radio device, device type, model, revisionlevel, purpose, use, power output, or other characteristics orcombination of characteristics, such as having a static location orbeing a device of a specified type that is intended for mobile use.Applicable classifier use policies can vary with the geographic locationof the device, with current or anticipated speed of movement of thedevice, with time of day, time of year, with power transmissionlimitations of the device, with network access by the device, withremaining battery power, and/or other conditions of the DSA radioitself. Additionally, applicable classifier use policies can vary withcurrent situational conditions such as the presence of RF interference;terrain effects such as buildings, mountains, or the like preventingline or sight access to a transceiver; with local restrictions to theuse of specific radio frequencies or ranges of frequency; or otherfactors that may be dictated by the policy or that may be inferred fromhistorical data, detector signals, or classifier results.

Policies can use rules, or any other method, to specify attributes ofdevices for use in determining whether specific policy elements apply.Attributes can comprise specific hardware or firmware characteristics,such as a unique device ID, device capabilities such as the availabilityof Wi-Fi or Bluetooth, or information or capabilities present in thedevice, such as specific classifiers, certificates, spectrum databasedata, policy, or configuration parameter settings.

Policy requirements in may include at least a capability to specifyclassifiers that are not permitted for classification of detectedsignals. Such a capability can be provided through specification ofclassifiers that are permitted, with all others being prohibited, byspecification of classifiers that are not permitted, with all othersbeing permitted, or by specification of both permitted and not permittedclassifiers. Specification of classifiers can be accomplished by listingthe signal types that can be classified by the classifiers being sospecified (e.g. 802.11 Wi-Fi, LTE, Weather Radar, or TV), by namingclassifiers explicitly (e.g. manufacturer, software name and version,etc.), by listing the types of classification methods used (e.g.cyclostationary analysis, pilot signal identification, etc.), bycombinations of these or other methods, or by other means as will beknown to those with skill in the art.

In addition to policy-controlled classifier specification, spectrum useefficiency can be enhanced by a policy that includes elements thatspecify limits on classifier restriction so that restrictions are onlyimposed where and when necessary. For example, policy restrictions onclassifier use that vary with location, speed, direction of travel, timeperiod, device type, device model, device capabilities, specificauthorization being granted, frequency band, possession of one or moredigital certificates, group or network membership, locations of knowntransmitters, and/or frequency use (e.g. by use of a database of primaryuser sites and frequencies), or combinations of these and/or otherfactors, may be used. Such policy capabilities can be supported by useof known policy specification, distribution, and update methods as willbe well understood by those with skill in the art. These methods may beparticularly useful when policy requirements vary with location, whenpolicy varies over time, when policy varies by DSA network, or when thetiming of restrictions on classifier use is not known in advance or isof an unpredictable nature that requires dynamic policy adjustments toprevent unacceptable interference with primary users.

A policy may include elements used to specify one or more classifieroperational parameters, such as thresholds for use in determination ofsignal presence in a signal classification algorithm.

In some illustrative embodiments, one or more DSA devices can providelocally sensed environmental information, such as spectrum use, RFinterference levels, or types of signals being detected, to a centralcoordination site where such collected information is used at least inpart to adjust policies that are then distributed to some or all of theone or more DSA devices as necessary. A central coordination site canhave access to information not available to DSA devices that may beuseful for adjusting policy requirements so as to maximize efficiency ofspectrum use while maintaining protections against unacceptableinterference with primary users, or for any other purpose or purposes,such as creation or adjustment of RF exclusion zones, or to implement aset of apparently arbitrary policy changes in order to obfuscate whenprimary users, such as government or military, are actually operating ina given area. For example, a classifier on a DSA device may classifyWi-Fi signals on a particular channel as secondary user signals, but thecentral coordination site has information that a primary user iscurrently operating in the same area and legitimately using assigneespectrum to transmit signals in a manner that can be classified by atleast some classifiers as a Wi-Fi signal, when they are not Wi-Fisignals. To prevent interference with this primary user, the centralcoordination site can adjust policy to prohibit use of those classifiersthat can mistake the primary user signal for a Wi-Fi signal and to treatan unclassifiable signal as a primary user signal, and thus cause DSAdevices in the area that are using such classifiers to cease use of themand therefore be unable to classify the primary user signal and begintreating the unclassifiable signal as a primary signal. Such a policychange can result in actual Wi-Fi signals being treated as primary usersignals as well, but non-interference with primary user signals isparamount and this side-effect is of lesser importance. When the centralcoordination site receives information or otherwise determines that theprimary user is no longer operating in a manner that can be mistaken fora Wi-Fi signal, the policy can be adjusted again to remove therestriction.

Referring again to FIG. 3, the policy (3010) may be used by at least theclassifier scheduler (3020) and the interference management component(3070), for the purposes detailed herein. Policy mused by any of theclassifiers (3030, 3040, & 3050) operating on the device, as determinedby the design and configuration of each such classifier. Inconfigurations that employ classifiers capable of using policy, thepolicy may be filtered through the classifier scheduler (3020), whichprovides or operates each classifier with the policy elements required.In other configurations that employ classifiers capable of using policy,the policy may be made available in whole to each classifier, and theclassifier determines which policy elements are relevant, if any. Intypical devices, policy will comprise additional policy elements andhave additional uses related to device operation that are not related tothe classifier policy aspects and uses described herein. Provided thatpolicy includes at least one classifier plan that is made accessible inimplementable form to the classifier scheduler and interferencemanagement components, and in some cases one or more classifiers, thespecific form and any additional aspects of policy generally are notrelevant to embodiments of the current invention disclosed herein otherthan as specifically indicated.

Classifier plans specified by policy may include requirements andlimitations for the operation of the classifier scheduler and interfacemanagement components. In configurations that use dynamic policyupdates, classifier plans also may be dynamically updated as part of adynamic policy update. Classifier plans can be incorporated, in whole orin part, into policy. Alternatively or in addition, classifier plans, orportions thereof, can be referenced by policy and obtained from thereferenced source or sources (e.g. by URL and an HTML GET operation, byfilename and file read operation, by policy server node address and apolicy request, etc). Classifier plans also can be specified by a uniqueidentifier and accessed from one or more known sources by use of theunique identifier. For example, classifier plans may be accessed from apolicy cache, a list of policies or policy references indexed by theunique identifier, or by a search of one or more known classifier plansources using the unique identifier as a search key. Alternatively or inaddition, classifier plans may be specified by capability, such as“capability to identify LTE signals”, “capability to identify 802.11signals”, etc. and any available classifier plan, or combination ofplans, meeting the specified capability requirements are acquired andimplemented. In additional illustrative embodiments, combinations of twoor more of the above methods are used, such as a unique identifier thatspecifies an entry in a list of policy references, or a classifier planmade up of a classifier plan incorporated into policy in combinationwith a classifier plan acquired through a reference.

Classifier plans can be organized by policy into a hierarchy, whereplans higher in the hierarchy supersede those lower in the hierarchywherever there is a conflict. For example, if a higher level planprohibits the use of classifiers capable of classifying TV signals, anda lower level plan specifies use of a specific classifier forclassification of TV signals, the specific TV classifier will bedisabled by a classifier scheduler implementing the combined classifierplan.

Classifier plans can be conditional. For example, a classifier plan canbe made conditional by making the policy element that specifies itconditional. Alternatively, the classifier plan itself can containconditional elements. Conditions can include, for example, date, time ofday, location, completion status of one or more other classifiers,device resource availability or utilization levels, the time since agiven classifier successfully classified a signal, and/or signal powerlevel, or any combination thereof. For example, the order (i.e.parallel, sequential, and order within a sequence of classifiers) can beconditional on available resources, or the enablement of classifiers candepend on the completion status of one or more previous classifiers, ora classifier can be enabled only if the signal power is above athreshold level.

A portion of an illustrative non-limiting policy specification that usesa form of the XML document standard to specify a classifier plan appearsbelow.

 1.  <classifier_restrictions>  2.   <time start=“20130824130000”end=“20130824170000”>  3.    <area loc=“38.925983 , −77.244795”radius=“1km”>  4.     <classifier match=“and” mode=“prohibit”>  5.     <select_type type=“cyclostationary”/>  6.      <select_signalsignal=“LTE”/>  7.     </classifier>  8.     <classifier>  9.     <select_name name=“DSA-Comm ver 1.4”/> 10.     </classifier> 11.   </area> 12.   </time> 13.  <time match=“2013??01??????”> 14.   <area> 15.     <classifier mode=“prohibit” ignore=“cert-5”> 16.     <select_signal signal=“Wi-Fi”/> 17.     </classifier> 18.   </area> 19.   </time> 20.  </ classifier_restrictions> 21. <classifier_schedule> 22.   <parallel priority=1> 23.    <classifiername=“TV_Classifier” mode=“permit”> 24.    <classifiername=“LTE_Classifier” mode=“permit”> 25.   </parallel> 26.  <sequentialpriority=2 halt=1> 27.    <classifiername=“Police_Classifier” mode=“permit”> 28.    <classifiername=“WeatherRadar_Classifier” mode=“permit”> 29.    <classifiername=“ApproachRadar_Classifier mode=“permit”> 30.   </sequential> 31. </classifier_schedule>

The above classifier plan policy elements specify two classifierrestrictions and a classifier schedule. The first restriction isspecified by lines 2 through 12, and the second by lines 13 through 19.The classifier schedule is specified by lines 21 through 31.

The first restriction applies during a time period beginning at 1 pm onAug. 24, 2013 and ending at 5 pm on the same day, and only to an areawithin 1 kilometer of latitude 38.925983, longitude −77.244795. Itspecifies that classifiers using cyclostationary analysis methods todetect LTE signals are prohibited in the specified area during thespecified time.

The second restriction applies at times matching the specified pattern.That is, any time of day on the first day of every month in the year2013. No specific area is specified; therefore, the restriction applieseverywhere. The restriction prohibits classifiers capable of classifyingWi-Fi signals. Line 15 includes an “ignore” attribute specifying thatthe classifier restriction can be ignored by devices that possessauthorization certification “cert-5”. This authorization certificationcould be a reference to a digital certificate useful to excusecompliance with the classifier restriction, for example, to permit theprimary user to continue to use Wi-Fi signal classifiers during the timethe restriction is active for others.

The classifier schedule specifies that “TV_Classifier” and“LTE_Classifier” are to be run in parallel, after which the“Police_Classifier”, “WeatherRadar_Classifier”, and“ApproachRadar_Classifier” are to be run sequentially, in that order,until one of them classifies the signal.

The specific example of a classifier schedule disclosed above isprovided as an illustrative example. Those of skill in the art willunderstand additional methods for specifying locations, times,priorities, classifier methods, authorizations, and other policyaspects, such as the use of “regular expressions” for specifyingmatching criteria, delta times for specifying relative points in time,and lists for specifying networks or specific devices. Other methods forspecifying classifier plans, or for incorporating other policycapabilities described herein, will be well understood by those withskill in the art.

The classifier scheduler may be a single component dedicated to carryingout the functions of a classifier scheduler. Alternatively, theclassifier scheduler may be one aspect of a single component thatprovides multiple functions within a device. Similarly, a classifierscheduler may include multiple components that collectively carry outthe functions of a classifier scheduler.

The classifier scheduler can be implemented as software loaded from anon-volatile storage medium into a processor suitable for execution ofthe instructions making up the classifier scheduler. Alternatively or inaddition, a classifier scheduler as disclosed herein can be implementedin hardware, such as by use of Field Programmable Gate Arrays (FPGAs) orApplication-Specific Integrated Circuits (ASICs). More generally, aclassifier scheduler can be implemented by any combination of hardwareand/or software components and techniques that in combination providethe classifier scheduler functionality described herein.

The classifier scheduler may interpret classifier plans and may operateto control the use and/or behavior of classifiers according to policy.The classifier scheduler can enable or disable use of any givenclassifier for identification of a signal. Enablement or disablement canbe dependent on a variety of factors, such as signal detector outputs,the current time, the current date, the location of the device,available device resources, outputs from other classifiers, historicalclassifier outputs, or any combination of these or other factors. Thefactors used to determine whether to enable or disable a givenclassifier can be specified by policy. Enablement of a classifier doesnot cause or require that the classifier be used. Rather, enablement ofa classifier as disclosed herein makes the classifier available for use.In some cases multiple classifiers may be enabled, though only a subsetof the enabled classifiers are used for classification. Disablement of aclassifier prevents its use while it is disabled.

A classifier may be configured to classify one or more types of signal.In some configurations, each classifier may be dedicated to a singlesignal type, though generally any combination of single-type andmultiple-type classifiers may be used within a single device or system.

A disabled classifier may not process a signal received by a device,thus reducing resource use and thereby improving the efficiency of thedevice. Similarly, a classifier may not produce any signalidentification output. Alternatively, a disabled classifier may producean output, but may have the signal identification output blocked frominput to an interference management component or other component of adevice, or may produce a signal identification output indicating thatthe signal was not identified. Alternatively, a disabled classifier maypartially or completely process a received signal, but may not produceany signal identification output, may have a signal identificationoutput blocked from input to an interference management or othercomponent, or may always produce a signal identification outputindicating that the signal was not identified.

An enabled classifier may process a signal until the signal isidentified, or until the classifier determines that the signal cannot beidentified by the classifier. If a signal is identified, the classifiermay produce a signal identification output indicating the type of signalidentified. When a signal is identified by a classifier, the classifiermay produce a signal identification output indicating which classifieridentified the signal. For example, a signal identification output mayinclude data that indicates the type of signal identified by theclassifier, as well as data that indicates the specific classifier thatidentified the type of signal. A classifier also may produce an outputindicating a confidence level for identification of the signal. Ingeneral, any combination of these signal identification output types maybe produced when a classifier identifies a signal.

An enabled classifier that fails to identify a signal may not produceany signal identification output, may produce a signal identificationoutput indicating that the signal was not identified, or may produce asignal identification output indicating a confidence level that thesignal cannot be identified by the particular classifier.

An enabled classifier may produce output that is sent to a classifierscheduler as disclosed herein, which may be used as a factor inenablement or disablement of the classifier. The classifier output alsomay be used by the classifier scheduler in conjunction with policy toselect a new classifier plan to implement. Classifier output can beproduced whether or not the classifier successfully identifies thesignal. For example, if a classifier is configured to determine whethera signal is amplitude modulated (AM), and it fails to identify a signalas an AM signal, it can produce output to the classifier scheduler thatcauses all AM signal-related classifiers to be disabled, thus saving theresources that might otherwise be consumed by AM signal-relatedclassifiers, and avoiding any potential misclassifications by AMsignal-related classifiers. In this way, both efficiency and accuracy ofclassification can be enhanced.

The enabling or disabling of classifiers by the classifier scheduler canvary over time, as specified by policy. For example, policy can specifythat a first classifier be used to classify LTE signals until 1 Jan.2014, after which a second classifier is to be used for classifying LTEsignals. This capability enables synchronization of classifier upgrades,for example to meet regulatory requirements. Another example might beuse of a first classifier from 6 am to 6 pm, and a second classifierfrom 6 pm to 6 am. Still another example can involve disabling faultyclassifiers, or classifiers that have become inappropriate under achanged regulatory policy, where specifying that a classifier may not beused after a specified date and time prevents its further use unless anduntil policy is changed to permit its use again. The enablement ordisablement of a first classifier is unconnected with the enablement ordisablement of any other classifier unless policy specifies otherwise.

In addition to controlling the enabled or disabled state of allclassifiers in accordance with classifier plans, the classifierscheduler also may specify and/or control the order of use, run-timepriority, timing of use, and resource allocation of classifiers.

Classifiers can be operated in parallel, such as though hardware support(e.g. multi-processor or multi-core hardware), by use of time-sharemethods, or a combination of both. Classifiers also can be operatedserially, with one classifier beginning processing when the priorclassifier processing has completed. Classifiers also can be operated ina series-parallel mode, with some classifiers operating in parallel andothers operating serially. The specific sequence in which classifiersare operated, and the requirements as to completion status of previousclassifiers for each classifier to begin processing, is specified by aclassifier plan. The requirements for completion status of previousclassifiers can include, for example and without limitation, that theclassifier has completed processing (i.e. classified the signal ordetermined that it cannot classify the signal), that the classifier hasclassified the signal, that the classifier has failed to classify thesignal, that the classifier has classified the signal with a confidencevalue above, or below, a threshold, that the classifier has failed toclassify the signal with a confidence value above, or below, athreshold, and that the signal has been classified as being of aparticular signal type (e.g. AM, FM, radar, 802.11, TV, etc).

Run-time priority refers to the relative percentage of availableprocessing time assigned to a particular classifier when classifiers areoperated in parallel in a time-share system. Classifiers with a higherrun-time priority are given a larger percentage of available processingtime than classifiers with lower run-time priorities. Assigning higherrun-time priorities to classifiers with a greater likelihood ofclassifying a signal can result in a quicker classification than wouldbe the case if such classifiers did not receive higher run-timepriorities. In embodiments where the classifier scheduler disablesclassifiers that failed to classify a signal when another classifiersuccessfully classifies the signal, the resources that would have beenused by the disabled classifiers are saved for other uses, thusimproving device efficiency.

A signal detector output may be used by the classifier scheduler as acontrol on classifier use. For example, when the signal detector outputindicates that there is no signal present, all classifiers can bedisabled, thus saving the resources otherwise consumed by theclassifiers. When the signal detector output indicates that a signal ispresent, classifiers can be enabled according to a classifier plan.

The signal detector may produce at least an output indicating whether asignal is present or a signal is not present. A signal detector also mayindicate a confidence value indicating how likely the signal present/notpresent output is to be correct, detected signal power levels, metadatasuch as the time the signal was first detected, direction from which thesignal arrived, etc. The output or outputs of the signal detector may beused by the classifier scheduler as factors in controlling the enablingand disabling of classifiers as described elsewhere herein. The signaldetector outputs also can be used by the interference managementcomponent as described elsewhere herein. Signal detection can be done byany methods known to those with skill in the art. For example, signaldetection may be performed by use of Fast Fourier Transforms to convertthe signal to a power spectrum, and examination of the bin values tolocate bins with higher than background power levels.

The interference management component may maintain interference levelsfor primary spectrum users at or below an acceptable level. This can bedone by various known means, such as selecting frequencies not in use byprimary users, reducing transmit power levels, making transmissionsdirectional and along paths that do not intersect with primary userreceivers, etc. Detection of primary user transmissions may be criticalto avoiding interference with primary users, while still sharing primaryuser frequency bands. Outputs from classifiers are usually used fordetection of primary user transmissions; however, in some cases, signaldetector output alone may be usable to support a channel selectiondecision. In some configurations, a policy may include elements thatalter channel selection choices based on detector output without using aclassifier. In one specific example operating mode, a detector signalalone may indicate that a detected signal on a particular channel orrange of channels exceeds an upper power amplitude limit for reliableuse. In this situation, the channel is unusable and there is no need toclassify the signal. In another example use mode, a detected signal mayhave a spectral bandwidth consistent with a particular signal type orprotocol such as Wi-Fi or a cellular communication protocol. In thiscase, a policy may dictate that the channel should be avoided withclassification or may dictate that a particular classifier associatedwith classifying the suspected signal type indicated by the detectorsignal characteristics be run first or exclusively. Classifier outputsand signal detector outputs may provide critical information to theinterference management component, enabling it to differentiate betweenempty spectrum, primary user use of spectrum, and secondary user use ofspectrum. The interference management component produces outputs usefulfor selecting, or controlling various aspects of device behavior, suchas transmission frequencies in use by the device, changes intransmission frequencies, transmission power levels, timing oftransmissions, directionality of transmissions, and coordination offrequency or channel use with other devices. The interference managementcomponent uses the classifier and signal detector outputs according topolicy requirements.

The above described capabilities may enable a number of usefulimprovements over the prior art. These include, but are not limited to,removal of outdated, malfunctioning, or inefficient classifiers fromservice; improved and flexible configuration of classifier use thatimproves efficiency and can reduce the time required to classify asignal; making classifier use location, time, device, device resource,and signal presence dependent; enabling a device to adapt its use of itsclassifiers to its current signal conditions and resource availabilityand load; and potentially reducing battery drain for mobile deviceswithout reducing classifier performance.

Using the above methods in conjunction with appropriate policies, a DSAdevice can avoid unacceptable interference with primary spectrum users,even when the primary users are behaving in a manner that mimics asecondary user, or in a manner that cannot be classified by availableclassifiers, such as by use of a new or proprietary signal type.Obsolete or malfunctioning classifiers can be removed from servicethrough policy changes, and classifier use patterns can be madeadaptable to the conditions being experienced by a DSA device, as wellas to its current capabilities and resources. These capabilities enhancethe efficiency of DSA devices, reduce unacceptable interference withprimary users, and can prolong battery life in some scenarios for mobiledevices.

4.1 Illustrative System Functionality

FIG. 4 is a diagram of an illustrative embodiment of the currentinvention processing a signal of a first frequency band. A frequencyband is defined by a lower frequency boundary and an upper frequencyboundary, and includes the frequency range between these boundaries. Theillustrative embodiment is similar to the device shown in FIG. 1, butwith the addition of a policy component (4010) that is used, at least inpart, to specify a classifier plan that is implemented by the classifierscheduler (4020) to enable or disable the classifiers (4030, 4040, &4050) used for analysis of the input signal (4090) as disclosed herein.The device also includes signal detection (4060) and interferencemanagement (4070) processing components. Signal detection (4060) may beuseful to determine whether a signal is present or not present.Interference management may be useful to determine whether mitigation ofinterference is required or not, and if mitigation is required, whatform it should take under the current policy. Options for mitigation arewell understood by those with skill in the art, and include, withoutlimitation, changing the frequency band in use, reducing transmittedpower levels, altering transmission direction away from primary usersites, and ceasing transmission.

The input (4090) is sent to the signal detection component (4060), whichdetermines that there is a signal present and outputs a “signal present”result (4065) to the interference management processing component(4070). The signal is also sent to the classifier scheduler (4020) whichuses the classifier plan supplied by policy (4010) to determine theclassifiers to enable (4030 & 4050) for classifying the signal under thecurrent circumstances (e.g. date, time, location, device resources,etc). The classifier prohibited by the current policy (4040) is disabledand/or not given the signal to process.

As another example, the signal may be supplied to all classifiers (4030,4040, & 4050), and each of the classifiers uses policy (4010) todetermine whether to classify the signal, and/or whether to output aresult. As another example, the signal may be given to all classifiers(4030, 4040, & 4050), which each output a result, and the results arefiltered according to policy (4010) such that only outputs from enabledclassifiers are supplied to the interference management processingcomponent (4070). As another example, the signal may be given to allclassifiers (4030, 4040, & 4050), which each output a result, and theinterference management processing component (4070) uses only theoutputs from classifiers enabled by policy (4010) in determining how tomanage interference.

In the example shown in FIG. 4, Classifier 1 (4030) identifies thesignal as a primary user signal (4035) to the interference managementprocessing component (4070), which determines that the proper responseis to vacate the frequency band (4080) since the signal was classifiedas being that of a primary user and policy (4010) in this case requiredvacating a frequency band that is in use by a primary user. Inalternative scenarios other actions may be required, such as reducingtransmitted power levels, controlling directionality, or other methodsof controlling interference with the primary user.

FIG. 5 is a diagram of an illustrative embodiment of the currentinvention processing a signal of a second frequency band. The signalinput (5090), signal detection (5060) and output indicating that asignal is present (5065) occur as previously described for FIG. 4. Inthe example shown in FIG. 5, Classifier 3 (5050) identifies the signalas a secondary user signal (5055). Classifier 1 (5030) does not classifythe signal, and classifier 2 (5040) is disabled by the classifier planof the current policy (5010). The decision of interference management(5070) is, therefore, not to vacate the frequency (5080) since thesignal is not that of a primary user.

FIG. 6 is a diagram of an illustrative embodiment of the currentinvention processing an input from a third frequency band (6090). In theexample shown in FIG. 6, there is no signal, so the signal detection(6060) output indicates that there is no signal present (6065).Classifier 2 (6040) is disabled due to the classifier plan of thecurrent policy (6010). The enabled classifiers (6030 & 6050) have noidentification outputs since there is no signal present (6065), and theinterference management processing (6070) therefore determines that nofrequency change (or other mitigating action) is required (6080).

FIG. 7 is a diagram of an illustrative embodiment of the currentinvention processing a signal of a fourth frequency band (7090). In theexample shown in FIG. 7, there is a signal, so signal detection (7060)outputs a result indicating that a signal is present (7065) to theinterference management processing component (7070). The policy (7010)however, prohibits use of Classifier 2 (7040), which is the classifierin this case that would have been able to classify the signal (7090).Classifier 1 (7030) and Classifier 3 (7050) are unable to classify thesignal, so no classification of the signal is made. The interferencemanagement processing component (7070) has no input as to the nature ofthe signal to use in determining whether interference management isneeded. Policy can specify the actions to take in such circumstanceshowever, such as assuming that an unknown signal is a primary user (i.e.use the safest assumption to avoid interfering with primary users) andthe interference management processor can therefore assume that theunknown signal is a primary user, and output a “vacate” result (7080)(or take other actions as specified by policy). The same result occurseven when all three classifiers (7030, 7040, & 7050) are enabled if thesignal is of a type that no available classifier can identify (i.e.classification would require use of a fourth classifier that is notavailable in the example of FIG. 7).

FIG. 8 is a flowchart of an example process according to an embodimentof the invention for determining whether to mitigate interference in afrequency band using classifiers sequentially, rather than in parallelas described above. The process (8000) first checks to see whether asignal is present (8010). This is done by a signal detection componentusing methods well known to those with skill in the art, such ascomputing a power spectrum and comparing the power at the frequencyagainst the noise floor and employing a threshold to determine signalpresence or absence. Additional processing may be performed, forexample, when power above the noise floor is detected in order toeliminate false signal detections from noise spikes, such as are causedby lightning, or man-made causes such as power transmission lines. Ifthere is no signal present (8010), the decision is that mitigation ofinterference in the frequency band is not required (8080) since there isno current primary user use of the frequency band.

If a signal is present (8010), then available classifiers that areenabled by the current classifier plan of the current policy are triedone after another until all have been tried, or the signal is classifiedto an acceptable confidence level. To carry out this processing, anuntried classifier is selected (8020). If there are no untriedclassifiers (8020), the signal is determined to be unclassifiable andpolicy determines any required actions. For example, policy can specifythat in the presence of an unclassifiable signal, an assumption shouldbe made that the signal is that of a primary user, and the decision isto perform mitigation of interference in the frequency band (8070). Ifthere is an untried classifier (8020), a check is made to see if its useis permitted by the current classifier plan (8030). If the classifier isdisabled by the current classifier plan (8030) the classifier is notused, and a check for another untried classifier is performed (8020). Ifthe classifier is enabled by the current classifier plan (8030) theclassifier is used to attempt classification of the signal (8040). Ifthe classifier was unable to classify the signal (8050), a check is madeto see if there is another untried classifier (8020). If the classifiersuccessfully classified the signal (8050) a check is made to see if thesignal is that of a primary user (8060). If the signal is that of aprimary user (8060), the decision is to perform interference mitigationin the frequency band (8070), otherwise, the decision is to not performinterference mitigation in the frequency band (8080).

It will also be recognized by those skilled in the art that, while theinvention has been described above in terms of preferred embodiments,examples, and configurations, it is not limited thereto. Variousfeatures and aspects of the above described invention may be usedindividually or jointly. Further, although the invention has beendescribed in the context of its implementation in a particularenvironment, and for particular applications (e.g. DSA device mitigationof interference with primary spectrum users), those skilled in the artwill recognize that its usefulness is not limited thereto and that thepresent invention can be beneficially utilized in any number ofenvironments and implementations where it is desirable to use policy tocontrol use of optional processing components, both as to theirenabled/disabled status as well as their order of employment.Accordingly, the claims set forth below should be construed in view ofthe full breadth and spirit of the invention as disclosed herein.

5 EXAMPLES OF USE

The following examples of use are provided to illustrate certain aspectsof the present invention and to aid those of skill in the art inpracticing the invention. These examples are in no way to be considereda limitation on the scope of the invention in any manner.

5.1 Military Radio Interference Avoidance

Detection and classification of well known and standardized signals,such as television, commercial broadcast radio, cell phones, and 802.11Wi-Fi, is well understood, but classification of some types of signals,such as military communications or sensing signals (e.g. radar), can beproblematic. Civilian signals generally use known frequencies, havepublished characteristics useful to identify them, and are detectableusing typical classifier methods. In the case of military signals,however, typical classifier methods are sub-optimal or evennon-functional. Military signal characteristics are generally notpublished, and may even be treated as national secrets. Militarycommunication and sensing signals, in order to achieve required levelsof accuracy, timing, and stealth, may use a wide range of frequencies,switch rapidly between frequencies, and use transmission patternsdesigned to mimic transmissions that might be expected in a given areaso as to blend in with civilian patterns of spectrum use. In addition tomilitary radars, there is potential for other primary user systems, suchas police, intelligence, or other investigative organizations, to makeuse of similar techniques. In some cases, civilian businesses that mayhave need to transmit RF in ways that are not easily detected or trackedalso may want to use these techniques. For example, a vehicle trackingand recovery system, such as Lojack (a product of LoJack Corporation ofCanton, Mass.) or police vehicle trackers, have need to transmit RF onoccasion, but doing so in a way that can be identified reduces theeffectiveness of these systems. By using unpublished or stealth methods,primary users can make their signals unclassifiable, or have them bemistakenly classified as secondary users making DSA use of spectrumassigned to a primary user, and thus prevent triggering secondary usersto vacate the frequencies being used or otherwise mitigate interference.This can result in unwanted, and in some cases unlawful, interferencewith such signals, making DSA radio co-existence problematic. Whereinterference with such signals must be avoided, the only current methodavailable is to block off the required spectrum from DSA use, whichdecreases the efficiency of spectrum use and is contrary to the goals ofDSA. In some cases such blocking of relatively large portions ofspectrum may be unnecessary and inefficient if, instead, such spectrumuse can be reliably detected to a degree sufficient to allow a DSAdevice or system to make use of the relevant region of spectrum withoutinterfering with these uses, even if the particular signal is notclassified. Thus, improved methods as disclosed herein for dealing withunclassifiable signals, or primary user signals that can be mistaken forsecondary signals, may be desirable to avoid this.

Avoiding interference with primary users that are employing stealthtechniques, such as mimicking secondary users, or which havecharacteristics that are not known widely enough for DSA devices to haveworking classifiers for them, may require that secondary user DSAdevices treat unclassifiable signals as primary users, and thatsecondary DSA devices be configured so as to ensure that stealthedprimary user transmissions are not classifiable even when DSA devicesincorporate classifiers capable of identifying the signals that thestealthed primary users are mimicking.

The first requirement can be met by configuring secondary user DSAdevices with policies that require vacating frequencies, or taking otheractions to mitigate interference, unless detected signals can bepositively identified as being of secondary user origin or signal-likenoise. In such a configuration, if a DSA device with such a policyrequirement detects a signal, and cannot identify it as a secondary usersignal or noise, it must assume the signal is from a primary user andchange frequencies or take other appropriate interference mitigatingaction, such as reducing transmitter power, directing its transmissionsaway from primary user sites, or ceasing transmitting.

The second requirement, configuration to ensure that the stealthedprimary user transmissions are not classifiable, can be met through useof a classifier plan specified in or by policy that controls classifieruse by DSA devices as described herein. The classifier plan can prohibituse of any classifier that is capable of classifying a signal of thetype that the primary user is mimicking By prohibiting use of suchclassifiers, the DSA radio will be rendered unable to classify thestealthed primary user signal, and due to the policy requirement totreat unclassifiable signals as primary user signals, will treat theunclassifiable signal as a primary user signal and vacate the frequencyor take other interference mitigating actions. This may cause a DSAdevice to vacate frequencies that are only being used by actualsecondary users of the type the prohibited classifier(s) are capable ofidentifying, but this is preferable to remaining on the frequency whenthe detected user is a primary user employing stealth methods.Specification of the classifiers that are permitted, and those that areprohibited, can be specified by classifier plans in policy that can varyfrom place to place, time to time, by frequency band, or otherwise so asto permit reserving only the spectrum needed by primary users during thetimes and in the places where this is needed (e.g. in Military OperationAreas (MOAs) during scheduled training) Policy specifications also canbe limited by device, device type, by groups of devices, or in otherways, such as possession of a digital certificate, so as to enable someDSA devices to classify the signals, while others are prevented fromdoing so, thus enabling military use of civilian devices when necessaryor desirable.

The invention claimed is:
 1. A device comprising: a radio receiverconfigured to generate a digital radio signal responsive toelectromagnetic energy detected in a selected radio frequency (RF)spectral band; a plurality of signal classifiers, each classifier of theplurality of signal classifiers configured to identify a type of RFsignal based upon the electromagnetic energy detected in the selected RFspectral band; and a classifier scheduler configured to controloperation of the plurality of signal classifiers, based upon aclassifier plan, by: selecting and operating a first signal classifierfrom the plurality of signal classifiers, and subsequently selecting andoperating a second signal classifier from the plurality of signalclassifiers based upon the classifier plan and an output of the firstsignal classifier.
 2. The device of claim 1, wherein the classifier planspecifies a restriction on use of at least one of the plurality ofsignal classifiers.
 3. The device of claim 2, wherein the classifierplan specifies that at least two of the plurality of signal classifiersare to be operated in parallel.
 4. The device of claim 2, wherein theclassifier plan specifies an order of use of the plurality of signalclassifiers.
 5. The device of claim 2, wherein the classifier plancomprises at least one restriction on use of at least one of theplurality of signal classifiers, the at least one restriction beingbased upon one or more conditions selected from the group consisting of:a location of the device; a movement speed of the device; a time of day;a time of year; a frequency; a frequency range; a completion status ofone or more of the plurality of classifiers; an availability of at leastone resource available to the device; an elapsed time since a classifiersuccessfully classified a signal; and a signal power level.
 6. Thedevice of claim 2, wherein the restriction on use of at least one of theplurality of classifiers specifies a classifier that is disabled.
 7. Thedevice of claim 2, wherein the classifier plan specifies an order of useof the plurality of classifiers based upon the likelihood that each ofthe plurality of classifiers will be successful in classifying a signal.8. The device of claim 2, wherein the classifier plan specifies at leastone operational parameter selected from the group consisting of: acapability of one of the plurality of classifiers; an identification ofone of the plurality of classifiers; an operational status of one of theplurality of classifiers; and an efficiency of operation of one of theplurality of classifiers.
 9. The device of claim 1, further comprising:an interference manager configured to determine if the selected RFspectral band is available for radio communication by the device basedupon an output of at least one of the plurality of signal classifiers.10. The device of claim 1, further comprising: a policy managerconfigured to provide policy information to the classifier schedule, thepolicy information describing at least one restriction on use of atleast one of the plurality of signal classifiers.
 11. The device ofclaim 1, further comprising a computer-readable data storage storing atleast one policy, wherein the policy manager is configured to update theat least one policy.
 12. The device of claim 1, wherein each of theplurality of signal classifiers is configured to receive data from adigital signal detector based upon the electromagnetic energy detectedin the selected RF spectral band, and wherein each of the plurality ofsignal classifiers is configured to identify the type of signal basedupon the data from the digital signal detector.
 13. The device of claim12, wherein the device further comprises the digital signal detector.14. The device of claim 1, further comprising a channel managerconfigured to select the selected RF spectral band.
 15. The device ofclaim 1, wherein the radio receiver comprises a transceiver.
 16. Thedevice of claim 1, wherein a first group of the plurality of signalclassifiers are configured to operate in parallel, and a second group ofthe plurality of signal classifiers are configured to operate in series.17. A method comprising: in a radio frequency (RF) communication device,receiving energy in a first region of RF spectrum; determining that theenergy in the first region of the RF spectrum indicates the presence ofa signal in the first region of the RF spectrum; selecting a firstclassifier from among a plurality of classifiers available in the RFcommunication device based upon a classifier plan; providing datadescribing the energy in the first region of the RF spectrum to thefirst classifier; receiving a first classifier output from the firstclassifier; and selecting a second classifier from among the pluralityof classifiers based upon the first classifier output and the classifierplan; providing the data describing the energy in the first region ofthe RF spectrum to the second classifier; receiving a second classifieroutput from the second classifier; and selecting a channel forcommunication by the RF communication device based upon the secondclassifier output.
 18. The method of claim 17, further comprising:updating the classifier plan to indicate that at least one classifier ofthe plurality of classifiers is restricted.
 19. The method of claim 18,wherein the at least one classifier is restricted due to at least onecondition selected from the group consisting of: a location of the RFcommunication device; a movement speed of the RF communication device; atime of day; a time of year; a frequency; a frequency range; acompletion status of one or more of the plurality of classifiers; anavailability of at least one resource available to the RF communicationdevice; an elapsed time since a classifier successfully classified asignal; and a signal power level.
 20. The method of claim 18, whereinthe at least one classifier is disabled.
 21. The method of claim 17,further comprising: receiving policy information describing at least onerestriction on use of at least one of the plurality of signalclassifiers; and selecting the first classifier further based upon thepolicy information.
 22. The method of claim 17, further comprising:receiving data from a digital signal detector; and selecting the firstclassifier further based upon the data received from the digital signaldetector.